Operation

Dayton Blower Sound Level

Here is a video-clip to provide an idea of the blower-noise after changing the motor to the 3,000rpm Dayton 4M093E. For context I provide a brief introduction with my voice, and I have my receiver on. I used the NIOSH iOS app to obtain these measurements, before we get to the video:

• 30S-1 with Dayton 3,000rpm motor change: 59 dB(A) 1-meter directly in front
• Listening to HF Radio, SSB voice: 65 dB(A) for my preferred Sound Level
• My living-room is a blissful 36 dB(A)

Video - Dayton Blower Start-up and Sound Level

Dial Lights After Warm-Up

The 30S-1 amplifier was designed with a 3-min delay before allowing High Voltage on the tube - the Eimac datasheet specifies at least this long. Mine is closer to 2-1/2 minutes, so I must pause before pushing the "ON" button. To let me know when this time-delay has completed, I re-wired my dial-lights to the DC circuit which is down-wind of the thermal delay-timer; the dial-lights will only turn on after the time-delay.

• remove the hot lead from lamp socket DS201
• Add a new lead from DS201 to the white-red-orange-green wire at the rear of the HV "OFF" switch, S208 (either contact)

Here is a 10-second video clip showing the dial-lights illuminating, after the time-delay:

Video - Dial Lights after Warm-Up

Spares and Servicing

I use the Power Supply Shelf for storing 2 sets of spare fuses, and a set of Bristol wrenches:

Contests: SSB and CW

I (casually!) entered Field Day 2020, and gave my newly-renovated 30S-1 a weekend shake-down run. To jump between modes, I left the 30S-1 in "SSB" mode - this meant I always had idling-current, and did not operate the amp in Class C for CW. The penalty: higher heat dissipation. The benefit: one less thing to think about.

Tuning

How often? How to tune?

Tuning And Frequency Changes

My personal answer to "How Often" revolves around changes in frequency: I feel I must retune if I change by 50kHz on 20-15-10, and every ~25kHz on 40-80. Beware - I view these as maximum (contest) changes in frequency, where the amp will become a bit stressed (higher dissipation), but not unduly. If things are slow, I may re-tweak much more-often... maybe every few kHz :-)

There is a second answer too, involving changes in power, but it's less-common. If the power-level is changed - 25% might be good guidance - then the (Plate Voltage) / (Plate Current) impedance changes, and the Pi-output network will need adjustment too - if only for the proper impedance transformation, supposing resonance isn't greatly affected.

How To Tune

• Plate Dip Method
• Screen Peak Method
• Maximum Smoke Method

The general principle: start with reduced-drive, then work up to your desired power-level. Never let things get out-of-hand. For the 30s-1 and the 4CX1000A tube, stick to 0 grid-current! Normally, with a good tube, you will neither need it, nor have it; decrepit tubes may show notable grid-current which will seal their fate :-(

The 30S-1 was originally designed for 1kW DC input; given it's efficiency, this may produce 600W output, meaning 400W dissipated in the 4CX1000A tube. This is further reduced by your Mode - the duty-cycle / duty-factor will reduce the tube-dissipation even futher. Very Conservative! On the other hand, environmental factors like elevation will drastically reduce the cooling ability, and the normally-conservative 30S-1 design will become borderline :-O :-(

The takeaway: factor in your entire situation, if you even blink-think about striving for increased output

---

Plate Dip Method
This is always a good, safe method:

• LOADING control CCW (low numbers)
• MODE in SSB (far-right toggle switch UP)
• TRANSMIT: No-drive BIAS should give you 200mA idle Plate Current (maybe 250mA if you use a 4CX1500B and want improved linearity).
• DRIVE increase slightly to give some Plate Current, then quickly
• TUNE knob adjusted to give a Plate Current dip (resonance)
• DRIVE & LOADING are alternately increased, then Re-DIP often, and quickly
• Plate Current held to 300mA - 350mA, which is about the rated 1kW DC input it was designed for. You're done when you hit this desired Plate Current. If you have a Wattmeter, it should have a healthy reading (in the neighbourhood of 600W, maybe) and it should have shown approximately a peaking as you dip the plate.

This same method works with transmitters using tube-finals. For several decades, I used Heathkit, Yaesu, my own home-built transmitters, several amplifiers and other radios from the 60's and 70's - this was the manufacturer's described method of tuning too.

---

Screen Peak Method
My favourite! This method is a bit tricky until you are accustomed to it, but gives the sharpest, most-accurate tuning, and is the most tube-friendly. It relies on the fact that tetrode operating-conditions can be clearly seen in the behaviour of the Screen Current. And fortunately for us, Collins included Screen Current metering!! It is also helpful for you to understand that the Screen Current is OK to flow in or out of the tube... both directions of Screen Current are possible and do happen (the Screen Supply must be able to source and also sink current).

• LOADING control CCW (low numbers)
• MODE in SSB (far-right toggle switch UP)
• TRANSMIT: No-drive BIAS should give you 200mA idle Plate Current (maybe 250mA if you use a 4CX1500B and want improved linearity).
• DRIVE increase slightly to give some Plate Current, then quickly
• TUNE knob adjusted to give a Screen Current PEAK This peak could be any value; often the meter begins by reading hard-left (below 0), and a "peak" is any indication higher than this.
• DRIVE & LOADING are alternately increased, then Re-PEAK Screen Current. At some point, you may find the Screen Current hard-right; this is a sure indication to focus on LOADING adjustment, to reign Screen Current back in closer to '0'
• Your Goal: to get your desired Plate Current / Output Power, and find a LOADING point that produces a TUNING peak of 0. You are a puppet-master :-)

Too much drive when the amp is not loaded heavily enough will cause the screen current to go very high. Load the amp more by reducing the LOADING Capacitance (turn knob clock-wise / higher numbers)

This can seem challenging at times, because it's sensitive to your antenna-impedance, the Pi-output-network settings, Plate Voltage and Plate Current. But when you get it, you can feel great knowing that the tube impedance is transformed nicely to (conjugately) match whatever craziness your antenna presents, and the output-power is maximized.

---

Maximum Smoke Method
This tongue-in-cheek term really means "peak for maximum output". It's fast, it's simple, and for modest in-band frequency changes, it's a reasonable way to tweak and re-adjust the 30S-1. It's just not a great primary-tune-up method.

• LOADING control CCW (low numbers)
• MODE in SSB (far-right toggle switch UP)
• TRANSMIT: No-drive BIAS should give you 200mA idle Plate Current (maybe 250mA if you use a 4CX1500B and want improved linearity).
• DRIVE increase slightly to give some Plate Current, then quickly
• TUNE knob adjusted to give Maximum RF Output as shown on your wattmeter, neighbour's RFI, whatever :-)
• Successively tweak LOADING, DRIVE power, and TUNING to achieve an output power you know is "about right", maybe based on prior experience. This could reasonably be 600W - 750W for a 4CX1000A, or as much as twice that for a 4CX1500B with raised Screen Voltage.

For the Maxium Smoke method, bear in-mind the tube-dissipation limits (affected by stock or modified blower), and the HV Power Supply - the HV power supply is good for 2200W ICAS / 1400W CCS... very robust for Collins' original 1kW DC input to the plate, but less-robust if you push harder, or operate high-duty-cycle / high-duty-factor modes.